On vs Off , Good vs Evil

Question 1

Why does clonal deletion occur in the thymus ?

Answer 1

some lymphocytes will recognise self antigens and these need to be removed.

Question 2

what does the thymic selection depend on ?

Answer 2

the affinity of the TCR for MHC

Question 3

describe positive selection

Answer 3

Selects for T cells which bind with moderate affinity for MHC
Ensures mature T cells can recognise MHC and antigen in periphery.

Question 4

describe negative selection

Answer 4

– Removes T cells that bind too strongly to MHC

– Ensures self-reactive T cells are clonally deleted

Question 5

when does the selection occur and what happens to the size of the thymus as the person increases in age ?

Answer 5

selection occurs when young so size of thymus should decrease in size as you get older.

Question 6

why are potentially harmful self reactive T cells removed ?

Answer 6

because they have high affinity for self-antigens presented by MHC

Question 7

are all the self antigens presented in the thymus ?

Answer 7

nope sex hormones aren’t

Question 8

will a mother and father have the same or different HLA classes ?

Answer 8

different

Question 9

what is a rhesus disease ?

Answer 9

mother has rhesus negative blood (RhD negative) and the baby in her womb has rhesus positive blood (RhD positive). If she’s pregnant with an RhD positive baby, the antibodies can cross the placenta, causing rhesus disease in the unborn baby.

Question 10

why is the peripheral tolerance required ?

Answer 10

Different mechanisms exist to ensure that mature T cells don’t activate inappropriately.

Question 11

what occurs if there is no co stimulatory signal and just a specific signal alone ?

Answer 11

the T cell will become anergic. When it becomes anergic it is still alive but the function is inactivated. Once a cell becomes anergic it is difficult for the cells function to be turned back on.

Question 12

what occurs if there is no specific signal and just co stimulatory signal alone ?

Answer 12

then there is no effect on the T cell as there is no antigen.

Question 13

what is required in order for a T cell to be activated ?

Answer 13

APC needs to be there which binds to the TCR , The co - stimulatory molecule needs to bound as well as the specific signal.

Question 14

what does the CTLA - 4 bind to and what does this occur in ?

Answer 14

binds to B7.1 and this leads to the inactive T cell

Question 15

what occurs if the CD4 binds to the correct MHC and TCR ?

Answer 15

then the T cell will become active

Question 16

the Treg cell will release IL-10 and TGF-B , what does this lead to ?

Answer 16

an inhibitory effect on the other T cells as they are inactivated.

Question 17

when does the peripheral tolerance occur ?

Answer 17

after the education has occured in the thymus and it is here that cells can be turned back on.

Question 18

what is central tolerance ?

Answer 18

this is when the deletion of cells occur due to them reacting to self , after this occurs they cannot be reactivated

Question 19

where does central tolerance occur for B and T cells ?

Answer 19

B in bone marrow

T in thymus

Question 20

what is peripheral anergy ?

Answer 20

this is when the cell is inactivated by weak signals without their co stimulus.

Question 21

where does peripheral anergy occur ?

Answer 21

in the lymphoid organs

Question 22

how do regulatory T cells operate ?

Answer 22

they inhibit other cells due to the use of cytokines and intercellular signals.

Question 23

where do regulatory T cells operate ?

Answer 23

in the secondary lymphoid organs and the site of inflammation

Question 24

what is functional deviation ?

Answer 24

this is the differentiation of regulatory T cells that limits the inflammatory cytokine secretion.

Question 25

where does induced cell death or apoptosis occur ?

Answer 25

in the lymphoid tissues and site of inflammation

Question 26

what happens if a cell escapes the clonal deletion in the thymus and isn’t tolerized in the peripheray ?

Answer 26

it can become activated and lead to allergies

Question 27

what an allergy ?

Answer 27

this is when an immune response occurs in response to a non harmful antigen that is commensal

Question 28

what happens to the jejunum in the gut when someone is gluten intolerant ?

Answer 28

they become broken down

Question 29

what occurs in asthma ?

Answer 29

the asthmatic airways become closed as the smooth muscle contracts

Question 30

list some autoimmune diseases?

Answer 30

type 1 diabetes 
MS
Chrons 
anemia Vitiligo 
arthritis

Question 31

what is an immunodeficiency ?

Answer 31

disorders prevent your body from fighting infections and diseases. This type of disorder makes it easier for you to catch viruses and bacterial infections.

Question 32

why do immunodeficiency occur ?

Answer 32

as the immune system homeostasis is disrupted and the immune system goes into underdrive.

Question 33

whats a primary immunodeficiency ?

Answer 33

one you were born as it is genetically inherited

Question 34

whats a secondary immunodeficiency ?

Answer 34

you acquire later in life which could be down to infections , metabolic dysregulation or one that is therapeutically induced.

Question 35

whats an autoimmune disease a result of ?

Answer 35

immune system reacting to own bodies cells